Catalyst for preparation of synthesis gas and process for preparing carbon monoxide

ABSTRACT

Disclosed are a catalyst for producing a synthesis gas using a carbon-containing organic compound as a raw material and a process for producing carbon monoxide. The catalyst for producing a synthesis gas is composed of a carrier formed of a metal oxide and at least one catalytic metal selected from rhodium, ruthenium, iridium, palladium and platinum and supported on the carrier and is characterized in that the catalyst has a specific surface area of 25 m 2 /g or less, in that the electronegativity of the metal ion of the carrier metal oxide is 13.0 or less and in that the amount of the supported catalytic metal is 0.0005-0.1 mole %, in terms of a metal, based on the carrier metal oxide. The process for producing carbon monoxide includes a step of reacting a carbon-containing organic compound with carbon dioxide in a pressurized condition to produce a synthesis gas, and a step of concentrating carbon monoxide in the thus obtained synthesis gas and is characterized in that the above-described catalyst is used as a catalyst in the synthesis gas producing step.

TECHNICAL FIELD

The present invention relates to a catalyst for producing a synthesisgas and to a process for the production of carbon monoxide.

BACKGROUND ART

A synthesis gas is a mixed gas containing hydrogen and carbon monoxideand is widely used as a raw material for the synthesis of ammonia,methanol, acetic acid, etc.

Such a synthesis gas may be produced by reaction of a hydrocarbon withsteam and/or carbon dioxide in the presence of a catalyst. In thereaction, however, carbon deposition reactions occur as side reactionsto cause carbon deposition which brings about a problem of catalystpoisoning.

The raw materials for the carbon deposition are a carbon-containingorganic compound used as a raw material and CO produced in situ. Thecarbon deposition is accelerated as the partial pressures of these rawmaterials increase. Therefore, it is possible to reduce the amount ofthe carbon deposition by increasing the feed amount of steam and carbondioxide while reducing the reaction pressure. In this case, however, itis necessary to excessively use steam and carbon dioxide in order toreduce the partial pressures of the carbon-containing organic compoundand CO, so that several disadvantages are caused. For example,consumption of heat energy required for preheating steam and carbondioxide increases. Further, costs for the separation of these gases fromthe product increase. Moreover, since a large reaction apparatus isrequired, the apparatus costs increase.

JP-A-5-208801 discloses a carbon dioxide-reforming catalyst containing aGroup VIII metal supported on high purity, super-fine single crystalmagnesium oxide. JP-A-6-279003 discloses a carbon dioxide-reformingcatalyst containing a ruthenium compound supported on a carrier composedof a compound of at least one alkaline earth metal oxide and aluminumoxide. JP-A-9-168740 discloses a carbon dioxide-reforming catalystcontaining rhodium supported on a carrier formed of a Group II-IV metaloxide or a lanthanoid metal oxide or a composite carrier composed of theabove metal oxide and alumina. The reaction experiments using thesecatalysts are performed under ambient pressure. At a high pressure,which is industrially significant, these catalysts show a high carbondeposition activity and, hence, are not satisfactory as industriallyapplicable catalysts.

Carbon monoxide is widely utilized as a raw material for the synthesisof industrial products by, for example, hydroformylation. Carbonmonoxide is generally produced by the reforming of methane with steamaccording to the reaction shown below to obtain a synthesis gas, fromwhich carbon monoxide is subsequently separated:

CH₄+H₂O H₂+CO.

In this reaction, however, only 1 mole of carbon monoxide is producedper 3 mole of hydrogen. Thus, the process for the production of carbonmonoxide is not efficient. In contrast, the reforming of methane withcarbon dioxide proceeds as follows:

CH₄+CO₂2H₂+2CO.

Thus, hydrogen and carbon monoxide are produced in an equimolar amountso that this process is more efficient than the reforming with steam. Inthis case, when carbon dioxide is added in excess relative to methane,carbon monoxide is produced from carbon dioxide and hydrogen by thefollowing reverse shifting reaction:

CO₂+H₂CO+H₂O,

so that the concentration of carbon monoxide in the product gas furtherincreases. Therefore, the reforming with carbon dioxide is effective inthe production of carbon monoxide. However, the product gas obtained bythis reaction has a composition in an equilibrium which favors thecarbon deposition, so that the catalyst used for this reaction causesconsiderable deactivation of the catalyst.

The objects of the present invention are:

(1) to provide a catalyst for use in a process for the production of asynthesis gas by reaction of a carbon-containing organic compound withsteam and/or carbon dioxide, which catalyst has suppressed carbondeposition activity;

(2) to provide a catalyst for use in a process for the production of asynthesis gas by reaction of a carbon-containing organic compound withoxygen, which catalyst has suppressed carbon deposition activity; and

(3) to provide a process which includes a step of reacting acarbon-containing organic compound with carbon dioxide to produce asynthesis gas, and a step of concentrating carbon monoxide in the thusobtained synthesis gas and which can produce carbon monoxide in aneconomically favorable manner by using a catalyst having suppressedcarbon deposition activity in the synthesis gas producing step.

Other objects of the present invention will be understood from thefollowing description of the specification.

DISCLOSURE OF THE INVENTION

The present inventors have made an intensive study to accomplish theabove-described objects and, as a result, have completed the presentinvention.

In accordance with the present invention there is provided a catalystfor producing a synthesis gas comprising a carrier formed of a metaloxide and at least one catalytic metal selected from rhodium, ruthenium,iridium, palladium and platinum and supported on said carrier,characterized in that said catalyst has a specific surface area of 25m²/g or less, in that the electronegativity of the metal ion of saidcarrier metal oxide is 13.0 or less and in that the amount of saidsupported catalytic metal is 0.0005-0.1 mole %, in terms of a metal,based on said carrier metal oxide.

The present invention also provides a process for producing carbonmonoxide, which comprises a step of reacting a carbon-containing organiccompound with carbon dioxide at an elevated temperature in a pressurizedcondition in the presence of a catalyst to produce a synthesis gas, anda step of concentrating carbon monoxide in the thus obtained synthesisgas, said process being characterized in that said catalyst comprises acarrier formed of a metal oxide and at least one catalytic metalselected from rhodium, ruthenium, iridium, palladium and platinum andsupported on said carrier, in that said catalyst has a specific surfacearea of 25 m²/g or less, in that the electronegativity of the metal ionof said carrier metal oxide is 13.0 or less and in that the amount ofsaid catalytic metal is 0.0005-0.1 mole %, in terms of metal, based onsaid carrier metal oxide.

The catalyst of the present invention is used for the production of asynthesis gas using a carbon-containing organic compound as a rawmaterial. In this case, the processes for producing a synthesis gasinclude various conventionally known processes, for example, (i) aprocess in which a carbon-containing organic compound is reacted withsteam, (ii) a process in which a carbon-containing organic compound isreacted with carbon dioxide, (iii) a process in which acarbon-containing organic compound is reacted with a mixture of steamwith carbon dioxide and (iv) a process in which a carbon-containingorganic compound is reacted with oxygen.

The catalyst of the present invention contains at least one catalyticmetal selected from rhodium (Rh), ruthenium (Ru), iridium (Ir),palladium (Pd) and platinum (Pt) supported on a carrier metal oxidehaving specific characteristics. In this case, the catalytic metal canbe supported in the form of a metallic state or in the form of a metalcompound such as an oxide.

The catalyst of the present invention is characterized in that thecatalyst has activity required for converting a carbon-containingorganic compound into a synthesis gas while exhibiting a function tosignificantly suppress side reactions of carbon deposition reactions.

The catalyst according to the present invention can significantlysuppress the carbon deposition reactions is characterized in that:

(i) the electronegativity of the metal ion of the carrier metal oxide is13.0 or less;

(ii) the catalyst has a specific surface area of 25 m²/g or less; and

(iii) the amount of the supported catalytic metal is 0.0005-0.1 mole %based on the carrier metal oxide. Such a catalyst having a considerablysuppressed carbon deposition activity has been first found by thepresent inventors.

The metal oxide used as a carrier may be a single metal oxide or a mixedmetal oxide. In the present invention, the electronegativity of themetal ion in the carrier metal oxide is 13 or less, preferably 12 orless, more preferably 10 or less. The lower limit is about 4. Thus, theelectronegativity of the metal ion in the carrier metal oxide used inthe present invention is 4-13, preferably 4-12. The electronegativity ofthe metal ion in the metal oxide in excess of 13 is not preferable,because carbon deposition occurs significantly.

The electronegativity of the metal ion in the metal oxide is defined bythe following formula:

Xi=(1+2i)Xo

wherein Xi: electronegativity of the metal ion

Xo: electronegativity of the metal

i: valence electron number.

When the metal oxide is a mixed metal oxide, an averageelectronegativity of the metal ions is used. The average value is a sumof the products of the electronegativity of each of the metal ionscontained in the mixed metal oxide by the molar fraction of thecorresponding metal oxide of the mixed metal oxide.

The electronegativity (Xo) of a metal is in accordance with Pauling. Theelectronegativity in accordance with Pauling is as shown in “W. J. MoorePhysical Chemistry, Vol. 1 translated by FUJISHIRO, Ryoichi”, 4thEdition, Tokyo Kagaku Dojin, p. 707 (1974), Table 15.4.

The electronegativity of metal ion in a metal oxide is described indetail in, for example, “Syokubaikoza, vol. 2, p145 (1985) edited byCatalyst Society of Japan”.

The metal oxides may include those containing one or at least two metalssuch as Mg, Ca, Ba, Zn, Al, Zr and La. Illustrative of such metal oxidesare single metal oxides such as magnesia (MgO), calcium oxide (CaO),barium oxide (BaO), zinc oxide (ZnO), alumina (Al₂O₃), zirconia (ZrO₂)and lanthanum oxide (La₂O₃), and mixed metal oxides such as MgO/CaO,MgO/BaO, MgO/ZnO, MgO/Al₂O₃, MgO/ZrO₂, CaO/BaO, CaO/ZnO, CaO/Al₂O₃,CaO/ZrO₂, BaO/ZnO, BaO/Al₂O₃, BaO/ZrO₂, ZnO/Al₂O₃, ZnO/ZrO₂, Al₂O₃/ZrO₂,La₂O₃/MgO, La₂O₃/Al₂O₃ and La₂O₃/CaO.

The catalyst according to the present invention having a specificsurface area of 25 m²/g or less may be obtained by calcining a carriermetal oxide before the support of a catalytic metal at 300-1,300° C.,preferably 650-1,200° C. After the catalytic metal has been supported,the catalytic metal-supported carrier is further calcined at 600-1,300°C., preferably 650-1,200° C. It is also possible to obtain the catalystby supporting a catalytic metal on a carrier metal oxide, followed bythe calcination of the catalytic metal supporting product at 600-1,300°C., preferably 650-1,200° C. The upper limit of the calcinationtemperature is not specifically limited but is generally 1,500° C. orless, preferably 1,300° C. or less. In this case, the specific surfacearea of the catalyst or the carrier metal oxide can be controlled by thecalcination temperature and calcination time.

The specific surface area of the catalyst or the carrier metal oxideused in the present invention is preferably 20 m²/g or less, morepreferably 15 m²/g or less, most preferably 10 m²/g or less. The lowerlimit of the specific surface area is about 0.01 m²/g. By specifying thespecific surface area of the catalyst or the carrier metal oxide inwhich the electronegativity of the metal ion is 13 or less in the aboverange, the carbon deposition activity of the catalyst can besignificantly suppressed.

The amount of the catalytic metal supported on the carrier metal oxideis at least 0.0005 mole %, preferably at least 0.001 mole %, morepreferably at least 0.002 mole %, in terms of metal, based on thecarrier metal oxide. The upper limit is generally 0.1 mole %, preferably0.09 mole %. In the present invention, the amount of metal supported isdesirably in the range of 0.0005 -0.1 mole %, preferably 0.001-0.1 mole%.

In the catalyst of the present invention, the specific surface area ofthe catalyst is substantially the same as that of the carrier metaloxide. Thus, in the present specification, the term “specific surfacearea of a catalyst” is used as having the same meaning as “specificsurface area of a carrier metal oxide thereof”.

The term “specific surface area” referred to in the presentspecification in connection with a catalyst or a carrier metal oxide isas measured by the “BET method” at a temperature of 15° C. using ameasuring device “SA-100” manufactured by Shibata Science Inc.

The catalyst according to the present invention has a small specificsurface area and has an extremely small amount of a supported catalyticmetal so that the carbon deposition activity thereof is considerablysuppressed. Yet, the catalyst has satisfactory activity for converting araw material carbon-containing organic compound into a synthesis gas.

The catalyst of the present invention may be prepared by conventionalmethods. One preferred method of preparing the catalyst of the presentinvention is an impregnation method. To prepare the catalyst of thepresent invention by the impregnation method, a catalyst metal salt oran aqueous solution thereof is added to and mixed with an aqueousdispersion containing a carrier metal oxide. The carrier metal oxide isthen separated from the aqueous solution, followed by drying andcalcination. A method (incipient-wetness method) is also effective inwhich a carrier metal oxide is added with a solution of a metal saltlittle by little in an amount corresponding to a pore volume touniformly wet the surface of the carrier, followed by drying andcalcination. In these methods, a water soluble salt is used as thecatalyst metal salt. Such a water soluble salt may be a salt of aninorganic acid, such as a nitrate or a hydrochloride, or a salt of anorganic acid, such as an acetate or an oxalate. Alternately, a metalacetylacetonate, etc. may be dissolved in an organic solvent such asacetone and the solution may be impregnated into the carrier metaloxide. The drying is performed at a temperature of 100-200° C.,preferably 100-150° C. when the metal oxide is impregnated with anaqueous solution of a catalytic metal salt. When the impregnation isperformed using an organic solvent, the drying is performed at atemperature higher by 50-100° C. than the boiling point of the solvent.The calcination temperature and time are adequately selected accordingto the specific surface area of the carrier metal oxide or catalystobtained (the specific surface area of the catalyst). Generally, acalcination temperature in the range of 500-1,100° C. is used.

In the preparation of the catalyst of the present invention, the metaloxide used as a carrier may be a product obtained by calcining acommercially available metal oxide or a commercially available metalhydroxide. The purity of the metal oxide is at least 98% by weight,preferably at least 99% by weight. It is, however, undesirable thatcomponents which enhance carbon deposition activity or components whichare decomposed under reducing conditions, such as metals, e.g. iron andnickel, and silicon dioxide (SiO₂) . Such impurities in the metal oxideare desired to be not greater than 1% by weight, preferably not greaterthan 0.1% by weight.

The catalyst of the present invention may be used in various forms suchas powdery, granular, spherical, columnar and cylindrical forms. Theform may be appropriately selected according to the catalytic bed systemused.

The production of a synthesis gas using the catalyst of the presentinvention may be performed by reacting a carbon-containing organiccompound with steam and/or carbon dioxide (CO₂) or by reacting acarbon-containing organic compound with oxygen in the presence of thecatalyst. As the carbon-containing organic compound, a lower hydrocarbonsuch as methane, ethane, propane, butane or naphtha or a non-hydrocarboncompound such as methanol or dimethyl ether may be used. The use ofmethane is preferred. In the present invention, a natural gas (methanegas) containing carbon dioxide is advantageously used.

In the case of a method of reacting methane with carbon dioxide (CO₂)(reforming with CO₂), the reaction is as follows:

CH₄+CO₂2H₂+2CO   (1)

In the case of a method of reacting methane with steam (reforming withsteam), the reaction is as follows:

CH₄+H₂O 3H₂+CO   (2)

In the reforming with CO₂, the reaction temperature is 500-1,200° C.,preferably 600-1,000° C. and the reaction pressure is an elevatedpressure of 5-40 kg/cm²G, preferably 5-30 kg/cm²G. When the reaction isperformed with a packed bed system, the gas space velocity (GHSV) is1,000-10,000 hr⁻¹, preferably 2,000-8,000 hr⁻¹. The amount of CO₂relative to the raw material carbon-containing organic compound is20-0.5 mole, preferably 10-1 mole, per mole of carbon of the rawmaterial compound.

In the reforming with steam, the reaction temperature is 600-1,200° C.,preferably 600-1,000° C. and the reaction pressure is an elevatedpressure of 1-40 kg/cm²G, preferably 5-30 kg/cm²G. When the reaction isperformed with a packed bed system, the gas space velocity (GHSV) is1,000-10,000 hr⁻¹, preferably 2,000-8,000 hr⁻¹. The amount of steamrelative to the raw material carbon-containing organic compound is 0.5-5moles, preferably 1-2 moles, more preferably 1-1.5 moles, per mole ofcarbon of the raw material compound.

In the reforming with steam according to the present invention, it ispossible to produce a synthesis gas in an industrially favorable mannerwhile suppressing the carbon deposition, even when the amount of steam(H₂O) is maintained 2 moles or less per mole of carbon of the rawmaterial compound. In view of the fact that 2-5 moles of steam per moleof carbon in the raw material compound is required in the conventionalmethod, the catalyst of the present invention, which can permit thereforming reaction to smoothly proceed with an amount of steam of 2moles or less, has a great industrial merit.

The catalyst of the present invention is favorably used as a catalystfor reacting a carbon-containing organic compound with a mixture ofsteam and CO₂. In this case, the mixing proportion of steam and CO₂ isnot specifically limited but is generally such as to provide a H₂O/CO₂molar ratio of 0.1-10.

When a carbon-containing organic compound is reacted with oxygen usingthe catalyst of the present invention, the carbon-containing organiccompound may be such a hydrocarbon or non-hydrocarbon organic compoundas described previously and is preferably methane. As the source ofoxygen, there may be used oxygen, air or oxygen-rich air. In the presentinvention a natural gas (methane gas) containing carbon dioxide isadvantageously used as a reaction raw material.

In the case of the reaction of methane with oxygen, the reaction is asshown below:

CH₄+{fraction (1/20)}₂ CO+2H₂   (3)

In partial oxidation of the carbon-containing organic compound, thereaction temperature is 500-1,500° C., preferably 700-1,200° C. and thereaction pressure is an elevated pressure of 5-50 kg/cm²G, preferably10-40 kg/cm²G. When the reaction is performed with a packed bed system,the gas space velocity (GHSV) is 1,000-50,000 hr⁻¹, preferably2,000-20,000 hr⁻¹. The amount of oxygen relative to the raw materialcarbon-containing organic compound is such as provide a molar ratio ofcarbon of the raw material carbon-containing organic compound to oxygenmolecules C/O₂ of 4-0.1 mole, preferably 2-0.5 mole. Since the partialoxidation method is a greatly exothermic reaction, it is possible toadopt a reaction system of autothermic system while adding steam andcarbon dioxide to the raw material.

The above-described various reactions using the catalyst of the presentinvention may be carried out with various catalyst systems such as apacked bed system, a fluidized bed system, a suspension bed system and amoving bed system.

A process for the production of carbon monoxide according to the presentinvention includes, as a first step, a synthesis gas producing step. Thefirst step is carried out by reacting a carbon-containing organiccompound with carbon dioxide in the presence of a catalyst. In thiscase, the previously described catalyst is used as the synthesis gasproduction catalyst.

In the reaction of the carbon-containing organic compound with carbondioxide (reforming with CO₂), the reaction temperature is 500-1,200° C.,preferably 600-1,000° C. and the reaction pressure is an elevatedpressure of 1-40 kg/cm²G, preferably 5-30 kg/cm²G. When the reaction isperformed with a packed bed system, the gas space velocity (GHSV) is1,000-10,000 hr⁻¹, preferably 2,000-8,000 hr⁻¹. The amount of carbondioxide relative to the raw material carbon-containing organic compoundis 1-10 moles, preferably 1-5 moles, more preferably 1-3 moles, per moleof carbon of the raw material compound.

In the reforming with CO₂ according to the present invention, asynthesis gas can be produced in an industrially advantageous mannerwhile preventing carbon deposition, even when the amount of CO₂ ismaintained no more than 3 moles per mole of carbon of the raw materialcompound.

The above-described reforming with CO₂ may be carried out with variouscatalyst systems such as a packed bed system, a fluidized bed system, asuspension bed system and a moving bed system and is preferablyperformed using a packed bed system.

As a result of the above-described reforming with CO₂, a synthesis gascontaining hydrogen and carbon monoxide is obtained. When methane isused as a raw material, the synthesis gas has, for example, acomposition containing 10-30 vol % of H₂, 35-45 vol % of CO, 5-40 vol %of unreacted CO₂, 0-30 vol % of unreacted CH₄ and 5-20 vol % of H₂O.

In the second step of the present invention, the thus obtained synthesisgas is used as a raw material and carbon monoxide (CO) is concentratedtherefrom. The CO concentration may be carried out by a customarilyemployed CO concentration method such as a cryogenic separation and aabsorption method using an aqueous copper salt solution as an absorbent.

EXAMPLE

The present invention will be further described in detail below byexamples.

Catalyst Preparation Example 1

The particle size of aluminum oxide calcined at 650° C. for 1.5 h (hour)in air was adjusted to 0.27-0.75 mm. Thereafter, Ru was supported on thealuminum oxide by an impregnation method (incipient-wetness method) .This was further calcined at 1,000° C. in air to obtain a Ru-supportingAl₂O₃ catalyst (Ru content was 3.0×10⁻⁴ g per 1 g of Al₂O₃ and, in termsof molar amount, 0.03 mol %). The above impregnated material wasobtained by adding dropwise an aqueous solution of ruthenium(III)chloride extremely little by little to the calcined Al₂O₃, with mixingby shaking after each dropwise addition. The Ru concentration in theaqueous solution of ruthenium(III) chloride added dropwise was 0.05% byweight. The impregnated material was dried at 120° C. for 2.5 h in airand calcined at 1,000° C. for 1.5 h in the same atmosphere to obtain theRu-supporting Al₂O₃ catalyst (surface area: 18.6 m²/g). Theelectronegativity Xi of Al³⁺ of Al₂O₃ is 11.3.

Catalyst Preparation Example 2

The particle size of zirconium oxide calcined at 600° C. for 2 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Rh was supported on thezirconium oxide by an impregnation method. This was further calcined at970° C. in air to obtain a Rh-supporting ZrO₂ catalyst (Rh content was8.4×10⁻⁶ g per 1 g of ZrO₂ and, in terms of molar amount, 0.001 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) acetate extremely little by little tothe calcined ZrO₂, with mixing by shaking after each dropwise addition.The Rh concentration in the aqueous solution of rhodium(III) acetateadded dropwise was 0.0065% by weight. The impregnated material was driedat 120° C. for 2.5 h in air and calcined at 970° C. for 2 h in the sameatmosphere to obtain the Rh-supporting ZrO₂ catalyst (surface area: 8.6m²/g). The electronegativity Xi of Zr⁴⁺ of ZrO₂ is 12.0.

Catalyst Preparation Example 3

The particle size of magnesium oxide (magnesia) calcined at 600° C. for2 h in air was adjusted to 0.27-0.75 mm. Thereafter, Rh was supported onthe magnesium oxide by an impregnation method. This was further calcinedat 1,100° C. in air to obtain a Rh-supporting MgO catalyst (Rh contentwas 2.6×10⁻³ g per 1 g of Mg and, in terms of molar amount, 0.1 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) acetate extremely little by little tothe calcined MgO, with mixing by shaking after each dropwise addition.The Rh concentration in the aqueous solution of rhodium(III) acetateadded dropwise was 1.7% by weight. The impregnated material was dried at120° C. for 2.5 h in air and calcined at 1,100° C. for 2 h in the sameatmosphere to obtain the Rh-supporting MgO catalyst (surface area: 0.6m²/g). The electronegativity Xi of Mg²⁺ of MgO is 6.6.

Catalyst Preparation Example 4

Rh was supported on magnesium oxide (in the form of ⅛ inch pellets),calcined at 1,100° C. for 3 h in air, by an impregnation method. Thiswas further calcined at 400° C. in air to obtain a Rh-supporting MgOcatalyst (Rh content was 1.5×10⁻³ g per 1 g of MgO and, in terms ofmolar amount, 0.06 mol %). The above impregnated material was obtainedby soaking the calcined MgO pellets in an aqueous solution ofrhodium(III) acetate having a Rh concentration of 1.0% by weight forabout 3 h. The impregnated material was then dried at 120° C. for 2.5 hin air and calcined at 400° C. for 3 h in the same atmosphere to obtainthe Rh-supporting MgO catalyst (surface area: 0.7 m²/g). Theelectronegativity Xi of Mg²⁺ of MgO is 6.6.

Catalyst Preparation Example 5

Rh was supported on magnesium oxide (in the form of ⅛ inch pellets),calcined at 1,100° C. for 3 h in air, by an impregnation method. Thiswas further calcined at 1,000° C. in air to obtain a Rh-supporting MgOcatalyst (Rh content was 2.6×10⁻⁵ g per 1 g of MgO and, in terms ofmolar amount, 0.001 mol %). The above impregnated material was obtainedby soaking the calcined MgO pellets in an acetone solution ofrhodium(III) acetylacetonate having a Rh concentration of 0.017% byweight for about 3 h. The impregnated material was then dried at 120° C.for 2.5 h in air and calcined at 1,000° C. for 3 h in the sameatmosphere to obtain the Rh-supporting MgO catalyst (surface area: 0.6m²/g). The electronegativity Xi of Mg²⁺ of MgO is 6.6.

Catalyst Preparation Example 6

Rh was supported on magnesium oxide (in the form of ⅛ inch pellets),containing 5 mol % of calcium oxide and calcined at 1,100° C. for 3 h inair, by an impregnation method. This was further calcined at 950° C. inair to obtain a Rh-supporting CaO/MgO catalyst (Rh content was 7.5×10⁻⁴g per 1 g of CaO/MgO and, in terms of molar amount, 0.03 mol). The aboveimpregnated material was obtained by soaking the calcined CaO/MgOpellets in an aqueous solution of rhodium(III) acetate having a Rhconcentration of 0.5% by weight for about 3 h. The impregnated materialwas then dried at 120° C. for 2.5 h in air and calcined at 950° C. for 3h in the same atmosphere to obtain the Rh-supporting CaO/MgO catalyst(surface area: 0.8 m²/g) The average electronegativity Xi of the metalions of the carrier is 6.5.

Catalyst Preparation Example 7

Rh was supported on magnesium oxide (in the form of ⅛ inch pellets),containing 10 mol % of lanthanum oxide and calcined at 1,100° C. for 3 hin air, by an impregnation method. This was further calcined at 950° C.in air to obtain a Rh-supporting La₂O₃/MgO catalyst (Rh content was9.0×10⁻⁵ g per 1 g of La₂O₃/MgO and, in terms of molar amount, 0.006 mol%). The above impregnated material was obtained by soaking the calcinedLa₂O₃/MgO pellets in an acetone solution of rhodium(III) acetylacetonatehaving a Rh concentration of 0.1% by weight for about 3 h. Theimpregnated material was then dried at 120° C. for 2.5 h in air andcalcined at 950° C. for 3 h in the same atmosphere to obtain theRh-supporting La₂O₃/MgO catalyst (surface area: 0.8 m²/g). The averageelectronegativity Xi of the metal ions of the carrier is 6.7.

Catalyst Preparation Example 8

The particle size of magnesium oxide calcined at 1,000° C. for 1.5 h inair was adjusted to 0.27-0.75 mm. Thereafter, Rh was supported on themagnesium oxide by an impregnation method. This was further calcined at950° C. in air to obtain a Rh-supporting MgO catalyst (Rh content was2.6×10⁻⁴ g per 1 g of MgO and, in terms of molar amount, 0.01 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) acetate extremely little by little tothe calcined MgO, with mixing by shaking after each dropwise addition.The rhodium(III) acetate aqueous solution had a Rh concentration of0.17% by weight. The Rh-impregnated material was dried at 120° C. for2.5 h in air and calcined at 950° C. for 1.5 h in the same atmosphere toobtain the Rh-supporting MgO catalyst (surface area: 5.8 m²/g).

Catalyst Preparation Example 9

The particle size of magnesium oxide calcined at 920° C. for 2 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Ru was supported on themagnesium oxide by an impregnation method. This was further calcined at920° C. in air to obtain a Ru-supporting MgO catalyst (Ru content was1.5×10⁻³ g per 1 g of MgO and, in terms of molar amount, 0.06 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of hydrated ruthenium(III) chloride extremely little bylittle to the calcined MgO, with mixing by shaking after each dropwiseaddition. The rhodium(III) chloride aqueous solution had a Ruconcentration of 1.0% by weight. The Rh-impregnated material was driedat 120° C. for 2.5 h in air and calcined at 920° C. for 2 h in the sameatmosphere to obtain the Rh-supporting MgO catalyst (surface area: 9.6m²/g).

Catalyst Preparation Example 10

The particle size of magnesium oxide calcined at 300° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Ir was supported on themagnesium oxide by an impregnation method. This was further calcined at600° C. in air to obtain a Ir-supporting MgO catalyst (Ir content was4.8×10⁻³ g per 1 g of MgO and, in terms of molar amount, 0.10 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of iridium(IV) chloride extremely little by little tothe calcined MgO, with mixing by shaking after each dropwise addition.The iridium(IV) chloride aqueous solution had a Ir concentration of 3.2%by weight. The Rh-impregnated material was dried at 120° C. for 2.5 h inair and calcined at 600° C. for 3 h in the same atmosphere to obtain theIr-supporting MgO catalyst (surface area: 24.8 m²/g).

Catalyst Preparation Example 11

The particle size of magnesium oxide calcined at 500° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Pt was supported on themagnesium oxide by an impregnation method. This was further calcined at750° C. in air to obtain a Pt-supporting MgO catalyst (Pt content was4.8×10⁻³ g per 1 g MgO and, in terms of molar amount, 0.10 mol %). Theabove impregnated material was obtained by adding dropwise an aqueoussolution of chloroplatinic acid ([H₂PtCl₆]) extremely little by littleto the calcined MgO, with mixing by shaking after each dropwiseaddition. The chloroplatinic acid aqueous solution had a Ptconcentration of 3.2% by weight. The Pt-impregnated material was driedat 120° C. for 2.5 h in air and calcined at 750° C. for 3 h in the sameatmosphere to obtain the Pt-supporting MgO catalyst (surface area: 18.4m²/g).

Catalyst Preparation Example 12

The particle size of magnesium oxide calcined at 300° C. for 3 h in airwas adjusted to 1.2-2.5 mm. Thereafter, Rh was supported on themagnesium oxide by an impregnation method. This was further calcined at950° C. in air to obtain a Rh-supporting MgO catalyst (Rh content was1.0×10⁻³ g per 1 g of MgO and, in terms of molar amount, 0.04 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) acetate extremely little by little tothe calcined MgO, with mixing by shaking after each dropwise addition.The rhodium(III) acetate aqueous solution had a Rh concentration of0.68% by weight. The Rh-impregnated material was dried at 120° C. for2.5 h in air and calcined at 950° C. for 3 h in the same atmosphere toobtain the Rh-supporting MgO catalyst (surface area: 6.0 m²/g)

Catalyst Preparation Example 13

The particle size of magnesium oxide calcined at 930° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Ru was, supported on themagnesium oxide by an impregnation method. This was further calcined at970° C. in air to obtain a Ru-supporting MgO catalyst (Ru content was7.5×10⁻⁴ g per 1 g of MgO and, in terms of molar amount, 0.03 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of ruthenium(III) chloride extremely little by littleto the calcined MgO, with mixing by shaking after each dropwiseaddition. The ruthenium(III) chloride aqueous solution had a Ruconcentration of 0.50% by weight. The Ru-impregnated material was driedat 120° C. for 2.5 h in air and calcined at 970° C. for 3 h in the sameatmosphere to obtain the Ru-supporting MgO catalyst (surface area: 5.2m²/g).

Catalyst Preparation Example 14

The particle size of magnesium oxide calcined at 350° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Rh was supported on themagnesium oxide by an impregnation method. This was further calcined at1,050° C. in air to obtain a Rh-supporting MgO catalyst (Rh content was2.0×10⁻³ g per 1 g of Mg and, in terms of molar amount, 0.08 mol %). Theabove impregnated material was obtained by adding dropwise an aqueoussolution of rhodium(III) acetate extremely little by little to thecalcined MgO, with mixing by shaking after each dropwise addition. Therhodium(III) acetate aqueous solution had a Rh concentration of 1.3% byweight. The Rh-impregnated material was dried at 120° C. for 2.5 h inair and calcined at 1,050° C. for 3 h in the same atmosphere to obtainthe Rh-supporting MgO catalyst (surface area: 1.5 m²/g)

Catalyst Preparation Example 15

The particle size of magnesium oxide calcined at 950° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Ru was supported on themagnesium oxide by an impregnation method. This was further calcined at950° C. in air to obtain a Ru-supporting MgO catalyst (Ru content was2.5×10⁻⁴ g per 1 g of MgO and, in terms of molar amount, 0.01 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of ruthenium(III) chloride hydrate extremely little bylittle to the calcined MgO, with mixing by shaking after each dropwiseaddition. The ruthenium(III) chloride hydrate aqueous solution had a Ruconcentration of 0.17% by weight. The Ru-impregnated material was driedat 120° C. for 2.5 h in air and calcined at 950° C. for 3 h in the sameatmosphere to obtain the Ru-supporting MgO catalyst (surface area: 4.8m²/g). In this case, Ru was found to be supported as ruthenium oxide.

Catalyst Preparation Example 16

The particle size of magnesium oxide calcined at 300° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Rh was supported on themagnesium oxide by an impregnation method. This was further calcined at1,050° C. in air to obtain a Rh-supporting MgO catalyst (Rh content was2.3×10⁻³ g per 1 g of MgO and, in terms of molar amount, 0.09 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) acetate extremely little by little tothe calcined MgO, with mixing by shaking after each dropwise addition.The rhodium(III) acetate aqueous solution had a Rh concentration of 1.5%by weight. The Rh-impregnated material was dried at 120° C. for 2.5 h inair and calcined at 1,050° C. for 3 h in the same atmosphere to obtainthe Rh-supporting MgO catalyst (surface area: 2.0 m²/g). In this case,Rh was found to be supported as rhodium oxide.

Catalyst Preparation Example 17

The particle size of magnesium oxide calcined at 1,000° C. for 3 h in,air was adjusted to 0.27-0.75 mm. Thereafter, Rh was supported on themagnesium oxide by an impregnation method. This was further calcined at950° C. in air to obtain a Rh-supporting MgO catalyst (Rh content was1.5×10⁻⁴ g per 1 g of MgO and, in terms of molar amount, 0.006 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) acetate extremely little by little tothe calcined MgO, with mixing by shaking after each dropwise addition.The rhodium(III) acetate aqueous solution had a Rh concentration of 0.1%by weight. The Rh-impregnated material was dried at 120° C. for 2.5 h inair and calcined at 950° C. for 3 h in the same atmosphere to obtain theRh-supporting MgO catalyst (surface area: 5.6 m²/g).

Catalyst Preparation Example 18

The particle size of magnesium oxide calcined at 500° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Rh and Pt were supported onthe magnesium oxide by an impregnation method. This was further calcinedat 1,050° C. in air to obtain a Rh- and Pt-supporting MgO catalyst (Rhand Pt contents were 1.8×10⁻³ g and 4.8×10⁻⁴ g, respectively, per 1 g ofMgO and, in terms of molar amount, 0.07 and 0.01 mol %, respectively).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) and chloroplatinic acid([H₂PtCl₆])acetate extremely little by little to the calcined MgO, withmixing by shaking after each dropwise addition. The mixed aqueoussolution had Rh and Pt concentrations of 1.2% by weight and 0.32% byweight, respectively. The Rh- and Pt-impregnated material was dried at120° C. for 2.5 h in air and calcined at 1,050° C. for 3 h in the sameatmosphere to obtain the Rh- and Pt-supporting MgO catalyst (surfacearea: 1.4 m²/g)

Comparative Catalyst Preparation Example 1

The particle size of magnesium oxide calcined at 370° C. for 3 h in airwas adjusted to 0.27-0.75 mm. Thereafter, Rh was supported on themagnesium oxide by an impregnation method. This was further calcined at370° C. in air to obtain a Rh-supporting MgO catalyst (Rh content was2.6×10⁻³ g per 1 g of MgO and, in terms of molar amount, 0.10 mol %).The above impregnated material was obtained by adding dropwise anaqueous solution of rhodium(III) acetate extremely little by little tothe calcined MgO, with mixing by shaking after each dropwise addition.The rhodium(III) acetate aqueous solution had a Rh concentration of 1.7%by weight. The Rh-impregnated material was dried at 120° C. for 2.5 h inair and calcined at 370° C. for h in the same atmosphere to obtain theRh-supporting MgO catalyst (surface area: 98 m²/g).

Reaction Example 1

The catalyst (5 cc) obtained in Catalyst Preparation Example 1 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream to convert oxidized Rh into metallic Rh. A rawmaterial gas having a molar ratio of CH₄:CO₂=1:1 was then treated at atemperature of 850° C. and a pressure of 20 kg/cm²G and with GHSV(methane basis) of 4,000 hr⁻¹. The CH₄ conversion at 5 h after thecommencement of the reaction was 55% (equilibrium CH₄ conversion underthe experimental condition=55%), and the CH₄ conversion at 100 h afterthe commencement of the reaction was 54%. The term “CH₄ conversion”herein is defined by the following formula:

CH ₄ Conversion (%)=(A−B)/A×100

A: mole number of CH₄ in the raw material

B: mole number of CH₄ in the product.

Reaction Example 2

The catalyst (5 cc) obtained in Catalyst Preparation Example 2 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:CO₂=1:1 was then treated at a temperature of 870° C. and a pressureof 10 kg/cm²G and with GHSV (methane basis) of 2,000 hr⁻¹. The CH₄conversion at 5 h after the commencement of the reaction was 71%(equilibrium CH₄ conversion under the experimental condition=71%), andthe CH₄ conversion at 50 h after the commencement of the reaction was71%.

Reaction Example 3

The catalyst (5 cc) obtained in Catalyst Preparation Example 3 waspacked in a reactor to perform a methane reforming test.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:CO₂:H₂O=1:0.5:1.0 was then treated at a temperature of 850° C. and apressure of 20 kg/cm²G and with GHSV (methane basis) of 4,000 hr⁻¹. TheCH₄ conversion at 5 h after the commencement of the reaction was 61.5%(equilibrium CH₄ conversion under the experimental condition=62%), andthe CH₄ conversion at 400 h after the commencement of the reaction was61.0%.

Reaction Example 4

The catalyst (20 cc) obtained in Catalyst Preparation Example 4 waspacked in a reactor to perform a methane reforming test.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream to convert oxidized Rh into metallic Rh. A rawmaterial gas having a molar ratio of CH₄:CO₂:H₂O=1:0.5:1.0 was thentreated at a temperature of 850° C. and a pressure of 20 kg/cm²G andwith GHSV (methane basis) of 3,500 hr⁻¹. The CH₄ conversion at 5 h afterthe commencement of the reaction was 61.0% (equilibrium CH₄ conversionunder the experimental condition=62.0%), and the CH₄ conversion at 280 hafter the commencement of the reaction was 61.0%.

Reaction Example 5

The catalyst (20 cc) obtained in Catalyst Preparation Example 5 waspacked in a reactor to perform a test of reforming methane with H₂O.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:H₂O=1:2 was then treated at a temperature of 850° C. and a pressureof 20 kg/cm²G and with GHSV (methane basis) of 2,000 hr⁻¹. The CH₄conversion and the H₂/CO molar ratio of the product gas at 5 h after thecommencement of the reaction were 72.0% (equilibrium CH₄ conversionunder the experimental condition=71%) and 4.6, respectively, and the CH₄conversion at 280 h after the commencement of the reaction was 71.8%.

Reaction Example 6

The catalyst (20 cc) obtained in Catalyst Preparation Example 6 waspacked in a reactor to perform a test of reforming methane with H₂O.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄: H₂O=1:1 was then treated at a temperature of 850° C. and a pressureof 20 kg/cm²G and with GHSV (methane basis) of 5,500 hr⁻¹. The CH₄conversion and the H₂/CO molar ratio of the product gas at 5 h after thecommencement of the reaction were 52.2% (equilibrium CH₄ conversionunder the experimental condition=52.3%) and 3.8, respectively, and theCH₄ conversion at 250 h after the commencement of the reaction was52.0%.

Reaction Example 7

The catalyst (20 cc) obtained in Catalyst Preparation Example 7 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 920°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:CO₂=1:1 was then treated at a temperature of 850° C. and a pressureof 20 kg/cm²G and with GHSV (methane basis) of 4,000 hr⁻¹. The CH₄conversion at 5 h after the commencement of the reaction was 54.0%(equilibrium CH₄ conversion under the experimental condition=55%), andthe CH₄ conversion at 380 h after the commencement of the reaction was53.5%.

Reaction Example 8

The catalyst (5 cc) obtained in Catalyst Preparation Example 8 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream to convert oxidized Rh into metallic Rh. A rawmaterial gas having a molar ratio of CH₄:CO₂=1:1 was then treated at atemperature of 850° C. and a pressure of 20 kg/cm²G and with GHSV(methane basis) of 4,000 hr⁻¹. The CH₄ conversion at 5 h after thecommencement of the reaction was 55% (equilibrium CH₄ conversion underthe experimental condition=55%), and the CH₄ conversion at 320 h afterthe commencement of the reaction was 54%.

Reaction Example 9

The catalyst (5 cc) obtained in Catalyst Preparation Example 9 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄: CO₂=1:1 was then treated at a temperature of 870° C. and a pressureof 10 kg/cm²G and with GHSV (methane basis) of 6,000 hr⁻¹. The CH₄conversion at 5 h after the commencement of the reaction was 71%(equilibrium CH₄ conversion under the experimental condition=71%), andthe CH₄ conversion at 520 h after the commencement of the reaction was71%.

Reaction Example 10

The catalyst (5 cc) obtained in Catalyst Preparation Example 10 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:CO₂=1:1 was then treated at a temperature of 830° C. and a pressureof 5 kg/cm²G and with GHSV (methane basis) of 2,500 hr⁻¹. The CH₄conversion at 5 h after the commencement of the reaction was 73%(equilibrium CH₄ conversion under the experimental condition=73%), andthe CH₄ conversion at 100 h after the commencement of the reaction was71%.

Reaction Example 11

The catalyst (5 cc) obtained in Catalyst Preparation Example 11 waspacked in a reactor to perform a methane reforming test.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:CO₂:H₂O=1:0.5:0.5 was then treated at a temperature of 880° C. and apressure of 10 kg/cm²G and with GHSV (methane basis) of 3,000 hr⁻¹. TheCH₄ conversion at 5 h after the commencement of the reaction was 70%(equilibrium CH₄ conversion under the experimental condition=70%), andthe CH₄ conversion at 120 h after the commencement of the reaction was67%.

Reaction Example 12

Example 8 was repeated in the same manner as described except that steamwas used in lieu of CO₂. The CH₄ conversions at 5 h and 320 h after thecommencement of the reaction were 52% and 51%, respectively.

Reaction Example 13

The catalyst (5 cc) obtained in Catalyst Preparation Example 12 waspacked in a reactor to perform a test of partial oxidation of methane.

The catalyst was previously subjected to a reduction treatment at 850°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:O₂=1:0.5 was then treated at a temperature of 800° C. and a pressureof 20 kg/cm²G and with GHSV (methane basis) of 5,000 hr⁻¹. The CH₄conversion at 5 h after the commencement of the reaction was 55%(equilibrium CH₄ conversion under the experimental condition=56%), andthe CH₄ conversion at 200 h after the commencement of the reaction was53%.

Reaction Example 14

The catalyst (5 cc) obtained in Catalyst Preparation Example 13 waspacked in a reactor to perform a test of partial oxidation of methane.

The catalyst was previously subjected to a reduction treatment at 800°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:O₂=1:0.5 was then treated at a temperature of 750° C. and a pressureof 15 kg/cm²G and with GHSV (methane basis) of 4,000 hr⁻¹. The CH₄conversion at 5 h after the commencement of the reaction was 52%(equilibrium CH₄ conversion under the experimental condition=52%), andthe CH₄ conversion at 150 h after the commencement of the reaction was50%.

Reaction Example 15

The catalyst (5 cc) obtained in Catalyst Preparation Example 14 waspacked in a reactor to perform a test of partial oxidation of methane.

The catalyst was previously subjected to a reduction treatment at 1,100°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:O₂:H₂O=1:0.5:0.5 was then treated at a temperature of 1,000° C. anda pressure of 20 kg/cm²G and with GHSV (methane basis) of 5,000 hr⁻¹.The CH₄ conversion at 5 h after the commencement of the reaction was 93%(equilibrium CH₄ conversion under the experimental condition=94%), andthe CH₄ conversion at 100 h after the commencement of the reaction was93%.

Reaction Example 16

Using two interconnected reactors, an automthermal reforming test wascarried out. A raw material gas having a molar ratio of CH₄:O₂=1:0.25was fed to a first reactor with GHSV (based on a catalyst contained in asecond reactor) of 6,000 hr⁻¹ and subjected to a combustion reaction ata temperature of 950° C. and a pressure of 25 kg/cm²G. To the secondreactor, a gas discharged from the first reactor, oxygen and carbondioxide were added (molar ratio of CH₄ (as raw material CH₄ fed to thefirst reactor):O₂:CO₂=1:0.25:0.5), so that a reforming reaction wascarried out using the catalyst (5 cc) obtained in Catalyst PreparationExample 17. The catalyst was previously subjected to a reductiontreatment at 950° C. for 1 h in a H₂ stream. The reaction conditionsincluded a temperature of 850° C. and a pressure of 25 kg/cm²G. After 5h from the commencement of the reaction, the CH₄ conversion was 71.8%and the contents of H₂ and CO in the product gas were 33.8 mol % and30.0 mol %, respectively. The CH₄ conversion at 200 h after thecommencement of the reaction was 71.6%.

Reaction Example 17

Using two interconnected reactors, an autothermal reforming test wascarried out. A raw material gas having a molar ratio of CH₄:O₂=1:0.5 wasfed to a first reactor with GHSV (based on a catalyst contained in asecond reactor) of 5,000 hr⁻¹ and subjected to a combustion reaction ata temperature of 1,050° C. and a pressure of 25 kg/cm²G. To the secondreactor, a gas discharged from the first reactor and carbon dioxide wereadded (molar ratio of CH₄(as raw material CH₄ fed to the first reactor):CO₂=1:0.5) so that a reforming reaction was carried out using thecatalyst (5 cc) obtained in Catalyst Preparation Example 18. Thecatalyst was previously subjected to a reduction treatment at 850° C.for 1 h in a H₂ stream. The reaction conditions included a temperatureof 700° C. and a pressure of 20 kg/cm²G. After 5 h from the commencementof the reaction, the CH₄ conversion was 46.7% and the contents of H₂ andCO in the product gas were 19.6 mol % and 16.1 mol %, respectively. TheCH₄ conversion at 150 h after the commencement of the reaction was46.5%.

Comparative Reaction Example 1

A test of reforming methane with CO₂ was performed in the same manner asdescribed in Reaction Example 1 except that the catalyst (5 cc) preparedin Comparative Catalyst Preparation Example 1 was used. In this case,the CH₄ conversions at 5 h and 15 h after the commencement of thereaction were 40% and 8%, respectively.

Comparative Reaction Example 2

A test of reforming methane with H₂O was performed in the same manner asdescribed in Reaction Example 6 except that the catalyst prepared inComparative Catalyst Preparation Example 1 was used. In this case, theCH₄ conversions at 5 h and 20 h after the commencement of the reactionwere 45% and 10%, respectively.

Comparative Reaction Example 3

A reaction experiment was performed in the same manner as described inReaction Example 13 except that the catalyst prepared in ComparativeCatalyst Preparation Example 1 was used. In this case, the CH₄conversions at 5 h and 40 h after the commencement of the reaction were13% and 9%, respectively.

Reaction Example 18

The catalyst (5 cc) obtained in Catalyst Preparation Example 17 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream to convert oxidized Rh into metallic Rh. A rawmaterial gas having a molar ratio of CH₄:CO₂=1:3 was then treated at atemperature of 850° C. and a pressure of 25 kg/cm²G and with GHSV(methane basis) of 6,000 hr⁻¹. After 5 h from the commencement of thereaction, the CH₄ conversion was 86.1% (equilibrium CH₄ conversion underthe experimental condition=86.1%) and the CO/H₂ molar ratio of theproduct gas was 2.2. The CH₄ conversion at 280 h after the commencementof the reaction was 85.7%.

Reaction Example 19

The catalyst (5 cc) obtained in Catalyst Preparation Example 7 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:CO₂=1:5 was then treated at a temperature of 830° C. and a pressureof 20 kg/cm²G and with GHSV (methane basis) of 5,500 hr⁻¹. After 5 hfrom the commencement of the reaction, the CH₄ conversion was 95.7%(equilibrium CH₄ conversion under the experimental condition=95.8%) andthe CO/H₂ molar ratio of the product gas was 3.2. The CH₄ conversion at400 h after the commencement of the reaction was 95.4%.

Reaction Example 20

The catalyst (5 cc) obtained in Catalyst Preparation Example 9 waspacked in a reactor to perform a test of reforming methane with CO₂.

The catalyst was previously subjected to a reduction treatment at 900°C. for 1 h in a H₂ stream. A raw material gas having a molar ratio ofCH₄:CO₂=1:1 was then treated at a temperature of 800° C. and a pressureof 20 kg/cm²G and with GHSV (methane basis) of 4,000 hr⁻¹. After 5 hfrom the commencement of the reaction, the CH₄ conversion was 45.5%(equilibrium CH₄ conversion under the experimental condition=45.5%) andthe CO/H₂ molar ratio of the product gas was 1.6. The CH₄ conversion at150 h after the commencement of the reaction was 45.2%.

Comparative Reaction Example 4

Methane reforming with CO₂ was repeated in the same manner as describedin Reaction Example 20 except that 5 cc of the catalyst obtained inComparative Catalyst Preparation Example 1 was used. After 5 h from thecommencement of the reaction, the CH₄ conversion was 42.0% (equilibriumCH₄ conversion under the experimental condition=45.5%) and the CO/H₂molar ratio of the product gas was 1.7. The CH₄ conversion at 15 h afterthe commencement of the reaction was 5.0%.

CO Concentration Example 1

The synthesis gas obtained in Reaction Example 18 and having a CO/H₂molar ratio of 2.2 was concentrated by an absorption method using a CuClsolution acidified with hydrochloric acid as an absorbent, therebyobtaining concentrated CO having CO concentration of 96%.

The catalyst according to the present invention shows considerablysuppressed carbon deposition activity, while retaining activity requiredfor converting a carbon-containing organic compound into a synthesisgas. By using the catalyst of the present invention, therefore, asynthesis gas can be produced continuously with a good yield for a longperiod of time while preventing carbon deposition.

Further, the use of the catalyst of the present invention caneffectively suppress the carbon deposition even at a high pressure, sothat a small size apparatus of producing a synthesis gas can be used andthe device costs can be reduced.

In the process for the production of carbon monoxide according to thepresent invention, the above-described specific catalyst is used in asynthesis gas producing step. This catalyst shows considerablysuppressed carbon deposition activity while retaining the activityrequired for converting a carbon-containing organic compound into asysthesis gas. Therefore, the synthesis gas producing step of thepresent invention can continuously produce a synthesis gas for a longperiod of time with a good yield while preventing carbon deposition.

Further, the use of the catalyst of the present invention caneffectively suppress the carbon deposition even at a high pressure andwith a small amount of CO₂ feed, so that a small size apparatus ofproducing a synthesis gas can be used and the device costs can bereduced.

Moreover, since the synthesis gas obtained in the synthesis gasproduction step has a small content of CO₂, the concentration of CO canbe efficiently performed with a small-sized device.

What is claimed is:
 1. A catalyst for producing a synthesis gascomprising a carrier formed of a metal oxide and at least one catalyticmetal selected from rhodium, ruthenium, iridium, palladium and platinumand supported on said carrier, characterized in that said catalyst has aspecific surface area of 25 m²/g or less, in that the electronegativityof the metal ion of said carrier metal oxide is 13.0 or less and in thatthe amount of said supported catalytic metal is 0.0005 -0.1 mole %, interms of a metal, based on said carrier metal oxide.
 2. A catalystaccording to claim 1, wherein said catalytic metal is rhodium and/orruthenium.
 3. A catalyst according to claim 1 or 2, wherein theelectronegativity of the metal ion of said metal oxide carrier is 4-12.4. A catalyst according to any one of claims 1-3, wherein the specificsurface area of said catalyst is 0.01-10 m²/g.
 5. A catalyst accordingto any one of claims 1-4, wherein said metal oxide carrier is magnesiumoxide.
 6. A process for producing carbon monoxide, which comprises astep of reacting a carbon-containing organic compound with carbondioxide at an elevated temperature in a pressurized condition in thepresence of a catalyst to produce a synthesis gas, and a step ofconcentrating carbon monoxide in the thus obtained synthesis gas, saidprocess being characterized in that said catalyst comprises a carrierformed of a metal oxide and at least one catalytic metal selected fromrhodium, ruthenium, iridium, palladium and platinum and supported onsaid carrier, in that said catalyst has a specific surface area of 25m²/g or less, in that the electronegativity of the metal ion of saidcarrier metal oxide is 13.0 or less and in that the amount of saidcatalytic metal is 0.0005 -0.1 mole %, in terms of metal, based on saidcarrier metal oxide.
 7. A process according to claim 6, wherein saidcatalytic metal is rhodium and/or ruthenium.
 8. A process according toany one of claims 6 or 7, wherein the electronegativity of the metal ionof said metal oxide carrier is 4-12.
 9. A process according to any oneof claims 6-8, wherein the specific surface area of said catalyst is0.01-10 m²/g.
 10. A process according to any one of claims 6-9, whereinsaid metal oxide carrier is magnesium oxide.
 11. A process according toany one of claims 6-10, wherein said carbon-containing organic compoundis methane.